Changes in the population structure and sporulation behaviour of Phytophthora ramorum associated with the epidemic on Larix (larch) in Britain

Harris, Anna; Mullett, Martin; Webber, Joan

doi:10.1007/s10530-018-1702-7

Cited by 12 publications

(13 citation statements)

References 31 publications

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“…The sudden larch death/sudden oak death pathogen P. ramorum arrived as a series of diploid clones of a single mating type, each with its own intrinsic heterozygous signature (e.g. Mascheretti et al ., ; Gagnon et al ., ; Harris et al ., ), but each clone is now showing increasing homozygosity (Kasuga et al ., ; Dale et al ., ). The alder dieback pathogen P. × alni has spread as a nascent heteroploid species hybrid and is potentially highly heterozygous, but although it forms gametangia abundantly it is currently sterile and so reproduces clonally (Brasier et al ., ; Delcan & Brasier, ; Husson et al ., ).…”

Section: Discussionmentioning

confidence: 99%

Is there evidence for post‐epidemic attenuation in the Dutch elm disease pathogenOphiostoma novo‐ulmi?

Brasier

Webber

2019

Plant Pathology

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The first pandemic of Dutch elm disease (DED) in Europe and North America caused by the introduced Ophiostoma ulmi began in the early 1900s but declined unexpectedly in Europe from the 1930s onwards after killing 30–40% of the elms. Later a second pandemic caused by the much more aggressive Ophiostoma novo‐ulmi spread across the same areas and by 1990 most of Britain's c. 30 million mature elms had died. During the second pandemic, O. novo‐ulmi acquired debilitating viruses and changed from being largely clonal to highly heterogeneous through horizontal transfer of novel, sometimes deleterious, genes from O. ulmi. In the post‐epidemic period a new disease dynamic has emerged, with millions of small recruitment elms repeatedly attacked by sequential cycles of disease. This study investigated the possibility of pathogenic attenuation in O. novo‐ulmi as the epidemic has progressed. Isolates collected from the three original outbreak areas in Britain in 1982–3 (early post‐epidemic period) and 2011 (advanced post‐epidemic) were compared for two fitness components: pathogenic aggressiveness and in vitro growth rate. Mean aggressiveness of the 2011 isolates to clonal English elm (Ulmus procera) proved not to differ significantly from that of the 1982 isolates, either overall or within each outbreak area. Similarly, the mean growth rates of the 1982 and 2011 samples showed no differences. The implications of these findings are discussed in relation to the future of the current DED pandemic in Europe, the decline of the first pandemic, and the difficulty of drawing parallels between different tree–pathogen systems.

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Section: Discussionmentioning

confidence: 99%

Is there evidence for post‐epidemic attenuation in the Dutch elm disease pathogenOphiostoma novo‐ulmi?

Brasier

Webber

2019

Plant Pathology

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“…SLD has a serious impact on the UK larch industry. Landowners suffer from significant losses through the destruction of immature crops, implementation of biosecurity measures and decreased timber values as the market is flooded with surplus supplies of felled larch ( Harris 2014 ).…”

Section: Airborne Phytophthora Diseases Of Forests and Woodlandsmentioning

confidence: 99%

Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands

Jung

Pérez‐Sierra

Durán³

et al. 2018

persoonia

161

208

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Most members of the oomycete genus Phytophthora are primary plant pathogens. Both soil- and airborne Phytophthora species are able to survive adverse environmental conditions with enduring resting structures, mainly sexual oospores, vegetative chlamydospores and hyphal aggregations. Soilborne Phytophthora species infect fine roots and the bark of suberized roots and the collar region with motile biflagellate zoospores released from sporangia during wet soil conditions. Airborne Phytophthora species infect leaves, shoots, fruits and bark of branches and stems with caducous sporangia produced during humid conditions on infected plant tissues and dispersed by rain and wind splash. During the past six decades, the number of previously unknown Phytophthora declines and diebacks of natural and semi-natural forests and woodlands has increased exponentially, and the vast majority of them are driven by introduced invasive Phytophthora species. Nurseries in Europe, North America and Australia show high infestation rates with a wide range of mostly exotic Phytophthora species. Planting of infested nursery stock has proven to be the main pathway of Phytophthora species between and within continents. This review provides insights into the history, distribution, aetiology, symptomatology, dynamics and impact of the most important canker, decline and dieback diseases caused by soil- and airborne Phytophthora species in forests and natural ecosystems of Europe, Australia and the Americas.

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“…with recent emerging findings of P. ramorum in France (Département de la Santé des Forêts (DSF), 2017) and the United Kingdom (Harris, Mullett, & Webber, 2018;Webber, Mullett, & Brasier, 2010), the situation warrants for careful monitoring. However, P. ramorum was not detected in the surveyed areas neither in the bark nor soil samples.…”

Section: Discussionmentioning

confidence: 99%

Multispecies Phytophthora disease patterns in declining beech stands

2019

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Decline diseases are typically caused by complex abiotic and biotic interactions and characterized by a suite of symptoms indicative of low plant vigour. Diseased trees are frequently infected by Phytophthora, but the complex interactions between pathogen, host and the heterogeneous forest environment mask a comprehensive understanding of the aetiology. In the present study, we surveyed European beech (Fagus sylvatica) stands in Swiss forests with recent increases in bleeding lesions for the presence of Phytophthora. We used a combined approach of analysing soil and bark samples from trees displaying bleeding lesions and trees free from bleeding lesions. Soil baiting revealed a higher prevalence of Phytophthora spp. around trees with bleeding lesions than around trees without bleeding lesions. For the bark samples from bleeding lesions, we used several detection methods. Phytophthora spp. were detected in 74% of the trees by an immunological on‐site diagnostic kit, in 64% by a specific PCR assay, and 38% by isolation on selective media. All samples tested were negative for P. ramorum using qPCR. Overall, nine Phytophthora species were identified by ITS sequencing, the most common of which were P. plurivora, P. gonapodyides, P. × cambivora and P. syringae. We identified distinct species in bleeding lesions and the rhizosphere of the same host tree which suggests a multispecies Phytophthora disease patterns in these declining beech. Among the recovered species, P. × cambivora and P. × serendipita were identified as hybrid genotypes with the former abundant in bleeding lesions.

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Changes in the population structure and sporulation behaviour of Phytophthora ramorum associated with the epidemic on Larix (larch) in Britain

Cited by 12 publications

References 31 publications

Is there evidence for post‐epidemic attenuation in the Dutch elm disease pathogenOphiostoma novo‐ulmi?

Is there evidence for post‐epidemic attenuation in the Dutch elm disease pathogenOphiostoma novo‐ulmi?

Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands

Multispecies Phytophthora disease patterns in declining beech stands

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